The possibilities are endless.
What if the worlds of Sonic were something that could be explored in reality? These could be anywhere Sonic and friends have visited; Zones, stages, adventure fields, whatever!
What if you could visit one right now? Which ones would be the safest, and which the most dangerous? How long would you survive? Would you want to live in one? All aspects of the real world apply, including physics, health risks, and need for OXYGEN (can't go to space, bro).
Remember to be (kind of) realistic; I honestly don't think you'd last very long taking up residence at Chemical Plant Zone.